March 16, 2013 – Unprecedented Arctic Ozone Depletion: The picture above shows( Left) Ozone in the Earth’s stratosphere at an altitude of approximately 12 miles (20 kilometers) , near the peak of the Arctic ozone loss. Red colors represent high levels of ozone, while purple and grey colors (over the North Polar Region) represent very small ozone amounts. Right: chlorine monoxide – the primary agent of chemical ozone destruction in the cold polar lower stratosphere – for the same day and altitude. Light blue and green colors represent small amounts of chlorine monoxide, while dark blue and black colors represent very large chlorine monoxide amounts. The white line marks the area within which the chemical ozone destruction took place.
A NASA-led study has documented an unprecedented depletion of Earth’s protective ozone layer above the Arctic last winter and spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere.
The amount of ozone destroyed in the Arctic was comparable to that seen in some years in the Antarctic, where an ozone “hole” has formed each spring since the mid-1980s. The stratospheric ozone layer, extending from about 10 to 20 miles (15 to 35 kilometers) above the surface, protects life on Earth from the sun’s harmful ultraviolet rays.
The Antarctic ozone hole forms when extremely cold conditions, common in the winter Antarctic stratosphere, trigger reactions that convert atmospheric chlorine from human-produced chemicals into forms that destroy ozone. The same ozone-loss processes occur each winter in the Arctic. However, the generally warmer stratospheric conditions there limit the area affected and the time frame during which the chemical reactions occur, resulting in far less ozone loss in most years in the Arctic than in the Antarctic.
To investigate the Arctic ozone loss, scientists analyzed a comprehensive set of measurements. These included daily global observations of trace gases and clouds from NASA’s Aura and Calipso spacecraft; ozone measured by instrumented balloons; meteorological data and atmospheric models. The scientists found that at some altitudes, the cold period in the Arctic lasted more than 30 days longer than in any previously studied Arctic winter, leading to the unprecedented ozone loss. Further studies are needed to determine what factors caused the cold period to last so long.
The pictures imply that if winter Arctic stratospheric temperatures drop just slightly in the future, for example as a result of climate change, then severe Arctic ozone loss may occur more frequently.
The Arctic ozone loss occurred over an area considerably smaller than that of the Antarctic ozone holes. This is because the Arctic polar vortex, a persistent large-scale cyclone within which the ozone loss takes place, was about 40 percent smaller than a typical Antarctic vortex. While smaller and shorter-lived than its Antarctic counterpart, the Arctic polar vortex is more mobile, often moving over densely populated northern regions. Decreases in overhead ozone lead to increases in surface ultraviolet radiation, which are known to have serious adverse effects on humans and other life forms.
Although the total amount of Arctic ozone measured was much more than twice that typically seen in an Antarctic spring, the amount destroyed was comparable to that in some previous Antarctic ozone holes. This is because ozone levels at the beginning of Arctic winter are typically much greater than those at the beginning of Antarctic winter.
The long atmospheric lifetimes of ozone-depleting chemicals already in the atmosphere mean that Antarctic ozone holes, and the possibility of future severe Arctic ozone loss, will continue for decades.
This could have serious implications for the entire planet and life, as we know it, on Earth!
The Master of Disaster